Conventionally, because a cable may be connected to a board in which a signal wiring is mounted, various structures that connect a cable to a board have been proposed.
Incidentally, research and development for realizing high-speed transmission of, for example, 25 Gbps or more by using electrical transmission have recently been conducted. In the case where a cable is connected to a board, impedance mismatching may occur in a terminal processing unit with the cable and a connector contact at which solder joint is performed, or in the fitting portion between connectors. For example, impedance mismatching may easily occur when a stub is formed or a through-hole is formed in the board. Impedance mismatching is considered as interfering with high-speed transmission in electrical transmission. A conventional board structure is not intended for high-speed transmission, and is not suitable as a board for realizing high-speed transmission.
The followings are reference documents.
[Document 1] Japanese Laid-Open Patent Publication No. 06-021613 and
[Document 2] Japanese Laid-Open Patent Publication No. 2012-248653.